Self-drilling bolt and nut assembly

ABSTRACT

A self-drilling bolt and nut assembly includes a nut which has a window to permit visual inspection of the fastener thread upon engagement with the nut. The nut also includes a protective cap or receives a protective cap so that upon threadably engaging the fastener with the nut, the drill tip of the fastener is automatically received in the cap. The nut also has at one end a plurality of projections to enhance the locking engagement. The self-drilling bolt may have an integral washer and employ a clamping plate engageable against the washer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of U.S. Provisional PatentApplication No. 61/279,870 filed on Oct. 27, 2009, the entirety of whichis incorporated herein by reference.

BACKGROUND

This disclosure relates generally to fasteners which extend throughbores of adjacent members and receive a bolt for fastening together themembers.

For construction applications for which the present disclosure relates,a bore is conventionally drilled through the adjacent wood members whichare to be fastened together under a load. A bolt is then insertedthrough the bore of the members and secured by a washer and a nut. Thebolt is typically quite elongated to accommodate the substantialthickness, especially when the adjacent members are 2×4, 2×6 or 2×8beams and other relatively thick structural components.

SUMMARY

Briefly stated, a fastener/locking assembly comprises a self-drillingfastener, a nut and a cap. The fastener comprises a head and a shankextending from the head to a drill point. The shank has a firstunthreaded portion adjacent the head and a portion adjacent the drilltip having a thread. The nut comprises a body having at one end alocking surface. The body has a central bore defined by an internalsurface complementary to the thread. The opposite end of the nut has acap. Upon threadably engaging the fastener with the nut and advancingthe fastener relative to the nut, the drill point is received in thecap. The nut preferably includes a window and has at least two wings orother surface structure adapted for applying or receiving a torque.

The head portion may include an integral washer and a tapered transitionto the shank. The shank has a first unthreaded portion adjacent thehead. The first unthreaded portion has a uniform diameter and extends asubstantial longitudinal distance to a first threaded portion. A secondthreaded portion is spaced from the first threaded portion adjacent thedrill tip.

A nut, which may be of plastic or metal form, comprises a body having atone end a flange-like locking surface. The nut is adapted to threadablyengage the fastener and includes an integral protective cap which coversthe drill tip upon threadable engagement of the nut and the fastener.The body has a central bore defined by a surface complementary to thethreaded portion of the fastener and enclosed at one end by the cap. Thenut has a window which permits visual inspection of the thread uponengagement with the nut. A marking may be placed on the nut exterior inthe vicinity of the window to indicate a minimum thread engagement forproper locking. The exterior surface of the nut is configured to resistor permit application of torque. The nut may include a pair of wings.The locking surface includes an arcuate array of projections.

A clamping plate has a recess which receives the washer and is mountedto the fastener shank for clamping engagement upon installation. Thesurface of the plate opposite the recess has an arcuate array ofprojections.

The fastener thread pitches, in various embodiments, are 7.3 and 7.5threads per inch and are preferably less than 8.0 threads per inch. Thelength of the threaded portion and the drill portion is approximately 2inches. Various fastener lengths may be provided. A single nutconfiguration is suitable for the different length fasteners. numerousnut and cap configurations are employed.

In one embodiment, the nut has a generally cylindrical surface traversedby a circumferential retaining ring. The cap has a closed end and aproximate end traversed by an annulus, an interior wall of which has arecess which mates with the retainer ring to retain the cap with thenut. The locking surface of the nut comprises a plurality ofprojections.

In one embodiment, the fastener shank has a plurality of alternatingthreaded and unthreaded portions. During installation, a protective capseparates from the nut and is retainably mounted over the drill tip.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a self-drilling bolt and nut assemblyillustrated in an assembled form;

FIG. 2 is an enlarged fragmentary sectional view of the self-drillingbolt and nut assembly of FIG. 1;

FIG. 2A is a sectional view of the nut of FIG. 2, taken along line A-Athereof;

FIG. 3 is a side view, partly in diagram form, of the self-drilling boltof FIG. 1;

FIG. 4 is a side view, partly in diagram form and partly broken away, ofa self-drilling bolt (axially rotated 90° relative to FIG. 3);

FIG. 5 is an enlarged fragmentary view, partly in diagram form, of theself-drilling bolt of FIG. 4;

FIG. 6 is an enlarged end view, partly in diagram form, of theself-drilling bolt of FIG. 4;

FIG. 7 is an enlarged side view of the nut of FIG. 1;

FIG. 8 is a perspective view of the nut of FIG. 7;

FIG. 9 is a perspective view of a plate employed in the assembly of FIG.1; and

FIG. 10 is a bottom plan view of the plate of FIG. 10.

FIG. 11 is a side view of a second embodiment of a fastening assemblycomprising a self-drilling bolt assembled with a nut and cap;

FIG. 12 is a sectional view of the bolt/nut/cap assembly of FIG. 1;

FIG. 13 is an enlarged side view of a portion of the bolt as engagedwith the nut and cap of FIG. 12;

FIG. 14 is an enlarged side view of a portion of a self-drillingbolt/assembled with a third embodiment of a nut and a cap;

FIG. 15 is an enlarged side view of a portion of the self-drilling boltassembled with a fourth embodiment of a nut;

FIG. 16 is an enlarged side view of a portion of a self-drilling boltassembled with a fifth embodiment of a nut and cap;

FIG. 17A is a side sectional view illustrating an application of abolt/nut assembly for fastening a deck post;

FIG. 17B is a side sectional view illustrating an application of abolt/nut assembled for fastening a ledger;

FIG. 17C is a side elevational view illustrating an application of apair of bolt/nut assemblies for a bracing;

FIG. 17D is a side sectional view illustrating an application of thebolt/nut assembly for fastening a carrying beam;

FIG. 17E is a side sectional view illustrating an application of abolt/nut assembly in conjunction with fastening a carrying beam;

FIG. 17F is a side sectional view illustrating an application of abolt/nut assembly for fastening 2 plies of material;

FIG. 17G is a side sectional view illustrating an application of abolt/nut assembly for fastening together 3 plies of material;

FIG. 17H is a side sectional view illustrating an application of anut/bolt assembly for fastening together 4 plies of material;

FIG. 18 is an enlarged front view of a portion of a self-drilling boltthreadably engaged with a nut having a cap;

FIG. 19 is a central sectional view of the bolt, nut and cap of FIG. 18;

FIG. 20 is an enlarged front view of a portion of a self-drilling bolt,a nut and a cap with the bolt being further engaged with the nut;

FIG. 21 is a central sectional view of the bolt, nut and cap of FIG. 20;

FIG. 22 is an enlarged frontal view of another embodiment of a nut;

FIG. 23 is a sectional view of the nut of FIG. 22;

FIG. 24 is a front view of a portion of a self-drilling bolt threadablyengaged with a nut and a cap;

FIG. 25 is a central sectional view of the bolt, nut and cap of FIG. 24;

FIG. 26 is a front view of a portion of a self-drilling bolt engagedwith a nut having a fixed cap;

FIG. 27 is a central sectional view of the bolt, nut and fixed cap ofFIG. 26;

FIG. 28 is a front view of a portion of a self-drilling bolt and a nutwith the bolt threadably engaged with a nut;

FIG. 29 is a side view, partly broken away, partly in section and partlyin diagrammatic form, of a self-drilling bolt as may be employed in theassemblies of FIGS. 11-16, 18-21 and 24-28;

FIG. 30 is a left end view of the self-drilling bolt of FIG. 29;

FIG. 31 is a sectional view of another embodiment of a self-drillingbolt;

FIG. 32 is an enlarged sectional view of a nut which may be employed inconnection with the bolt of FIG. 31;

FIG. 33 is an enlarged side view of a washer employed with the nut ofFIG. 32; and

FIG. 34 is an enlarged bottom plan view of the washer of FIG. 33.

DETAILED DESCRIPTION

With reference to the drawings wherein like numerals represent likeparts throughout the several figures, a first embodiment of a fastenerassembly which is employed for fastening at least two members under aload is generally designated by the numeral 10. The fastener assembly 10is designed as an enhancement over a conventional lag bolt fastenerassembly and has numerous applications. The fastener assembly 10 can bevery efficiently installed and is capable of providing a reliableconnection of high integrity.

In the conventional lag bolt fastener assemblies to which the fastenerassembly 10 relates and is configured to replace for certainapplications, a bore is drilled through members to be joined. A bolt isinserted into the bore. A threaded end opposite the bolt head protrudesaway from the end of the bore. A nut is typically threaded and tightenedonto the bolt end to implement the connection. One or more separatewashers may also be typically employed to enhance the clamping/lockingconnection.

With reference to FIGS. 1-10, fastener assembly 10, in one assembledembodiment, comprises a self-drilling, self-tapping bolt 12, a nut 14with an integral protective cap 16 and a clamping plate 18 which mountsto the bolt and is retainably engaged at the underside of the head ofthe bolt during installation.

The self-drilling bolt includes a head 20 and a shank 30 which extendsfrom the head and terminates in a drill tip 32. The head includes a hexhead 22. Other torque receiving structures, such as sockets, Philipsslots, proprietary custom drive systems, etc., are possible. The headpreferably includes an integral washer 23. A conical transition 24 atthe underside of the washer extends toward the shank at an angle of 60°.The transition 24 tapers to the shank portion adjacent the underside ofthe head which has an elongated cylindrical non-threaded form with auniform diameter.

With additional reference to FIGS. 3 and 4, the shank has two threadedportions 34 and 36 which are traversed by an intermediate interruptedportion 38 of uniform diameter. The remaining portion of the shank ispreferably essentially unthreaded.

With additional reference to FIGS. 5 and 6, in one embodiment, themaximum diameter h_(D) of the hex head is 0.340 ins., the distance h_(d)between opposed hex faces is 0.309 ins., and the longitudinal projectionh_(t) of the hex head is 0.160 ins. The integral washer 23 has athickness w_(t) of 0.090 ins., and a diameter w_(d) of 0.560 ins. Thetransition extends a longitudinal length t_(l) of 0.070 ins.

The shank 30 has a uniform diameter D of 0.228 ins. for the unthreadedportion. The threaded portions 34 and 36 have a pitch of 7.3 threads perinch. The longitudinal lengths of the first thread portion l₁, theuninterrupted portion l₂ and the second thread portion l₃ adjacent thetip are 0.56, 0.63 and 0.090, respectively.

The major diameter M_(D) of the threads of portions 34, 36 in oneembodiment is 0.302 and 0.310 ins., respectively, and the minor diameterm_(d) of the threads is 0.201 ins.

The drill point 32 extends for a longitudinal length l₄ of 0.300 ins.and preferably has a half-point configuration.

The length of the fastener L for various standard lengths and thecombined length l of the portions 34, 36, 38 and tip 32 in inches is setforth in Table 1 below:

TABLE 1 LENGTH I LENGTH L 2.39 4.570 2.39 5.000 2.39 6.250 2.39 7.0002.39 8.000 2.39 10.000

The foregoing specifications for one example of bolt 12 arerepresentative of one embodiment. Other suitable self-drilling boltembodiments can also be employed. It should also be noted that for someembodiments, the threads will not be interrupted and the threadedportion will be continuous, and in some embodiments, fully threaded tothe drill point.

With reference to FIGS. 2 and 2A, the nut 14 and integral cap 16 arepreferably integrally formed from a plastic material. The nut body 40preferably includes, at one end, an enlarged flange-like portion 50 witha circular array of shallow teeth-like projections 52. The projections52 engage the member and ultimately function to resist rotation of thenut. The intermediate portion of the body is generally cylindrical. Thebody is centrally traversed by an axial throughbore 44 which has athreading groove complementary to that of the fastener, and includes aslightly tapered entry opening 45. A pair of contoured, wings 42 extendradially in opposed diametral relationship and axially from the enlargedportion 50. The wings 42 are adapted to apply torque and/or resist theapplication of torque to the nut.

The cylindrical body integrally tapers in step-wise fashion to adome-like cap 16. The throughbore 40 continues into the cap andterminates in a conical end cavity 72.

A window 46 in one side or opposed sides of the nut body has alongitudinal dimension and is dimensioned so that the threads of thefastener may be inspected from the exterior of the nut. A minimummarking 48, including a reference line, is preferably affixed to theoutside of the nut adjacent the window 46 so that sufficient threadingengagement can be assured.

With reference to FIGS. 2 and 7, a preferred set of nut/cap dimensionsas referenced to FIG. 2A is set forth in Table 2 below for the foregoingdimensioned fastener 10:

TABLE 2 DESIGNATION DIMENSIONS (ins.) D₁ 0.250 D₂ 1.770 D₃ .020 D₄ 1.330D₅ 1.300 D₆ 1.500 D₇ 0.450 D₈ 0.020

The tapped bore 44 is 7.3 threads per inch with a preferred majordiameter of 0.315 ins.

The foregoing specifications for one example of nut 14 compatible withthe specifications for bolt 12 are representative of one embodiment.Naturally, other nut specifications may be suitable.

It should be appreciated that the nut is adapted so that the threadedportion 36 adjacent the fastener tip threadably engages with the threadgrooves of the nut and penetrates sufficiently into the threaded bore ofthe nut so that the drill tip 32 is generally received in the conicalend cavity 72 at the underside of the cap 16. The cap 16 provides aprotective structure for the drill tip 32 which can have a relativelysharp point.

With reference to FIGS. 9 and 10, the clamping plate 18 may be formed ofplastic. Alternatively, the plate may be manufactured from steel,aluminum, zinc and other materials. The plate 18 has an enlargeddiameter and includes at its upper side, a recess 80 with a flat bottomsurface 81 which is adapted to receive the underside of the integralwasher 23 at the head and has an opening 84 so that the plate can beengaged at the underside of the transition 24 and the integral washer23. The underside of the plate 18, which is preferably a molded plasticmember, includes an arcuate or circular array of shallow teeth-likeprojections 82 which extend approximately the same distance as that ofthe projections 52 of the nut. Projections 82 also engage the adjacentfastened member upon installation to resist rotation of the plate 18. Inone embodiment, the diameter of the plate is 1.25 ins., the diameter ofopening 84 is 0.325 ins., and the projections 82 extend axially 0.020ins. The minimum diameter of the recess 80 or the diameter of surface 81is 0.57 ins. The projections 52, 82 function to enhance the clamping andlocking engagement of the members secured by the fastening assembly.

Fastener assembly 10, which preferably includes the self-drilling,self-tapping bolt 12 as described, does not require pre-drilling. Thebolt 12 receives the plate 18 and is torqued so that it threadablyengages and advances through the first member and then through thesecond member. The specially configured nut 14 is then threaded onto theprotruding bolt threads. After the bolt is torqued so that the headengages against the first member, the nut 14 is then tightened andtorqued and/or the bolt head is further torqued so that the nut firmlyengages against the surface of the second member while the plate 18concurrently engages against the first member. The projections 82, 52engage into the member surfaces. The cap 16 is provided to protectivelycover the pointed drill tip of the bolt.

The fastener assembly typically comprises a self-drilling, self-tappingbolt, a nut and a cap and may assume various forms as further described.The cap may be merely carried by the nut and/or be integral with thenut. A fastener assembly may employ various self-drilling fastener/nutconfigurations. For some applications, a cap is optional.

There are a number of other possible configurations for the nut andprotective cap. In some instances, the protective cap may be optional.As illustrated in FIGS. 11-13, a cap 116, which may be plastic orsimilar form, is mounted over the end of the nut 114 andcircumferentially extends around a protruding side surface. It should benoted that a plate may also be alternatively included in the assembly ofFIGS. 11 and 12.

A second form of a nut of a fastener assembly 210 is illustrated in FIG.14 wherein the nut 214 is configured to receive a more abbreviated cap216 which is mounted in place after the nut is tightened.

Another fastener assembly 310 illustrated in FIG. 15 comprises a nut 314which is not configured to receive a cap and the pointed end of thefastener, which extends beyond the end of the nut, is left in anunprotected, protruding form.

For the fastener assembly 410 in FIG. 16, the nut 414 has a fixed cap416. The cap is integrated with the nut and is constantly retained withthe nut. The end of the self drilling bolt is fully received within thecap 410.

Because each of the fasteners for the fastening assemblies 110, 210, 310and 410 employ a bolt 112 which is self-drilling and preferablyself-tapping, the drill end points of the fastener, if projecting beyonda nut, may present an exposed sharpened point which could proveinjurious in certain environments. Accordingly, for some of theapplications, a protective cap 116, 216 and 416 is preferably provided.

The fastener assemblies have a wide range of applications and areparticularly adapted to connect members under a load as illustrated inFIGS. 17A-17H. FIG. 17A shows a fastener assembly as employed to fastena deck post. FIG. 17B illustrates a fastener assembly as employed tofasten a ledger. FIG. 17C illustrates a pair of fastener assemblies asemployed to secure a corner brace to a pair of perpendicular members.FIGS. 17D and 17E show the fastener assembly as employed in connectionwith fastening members to carrying beams. FIGS. 17F-17H show a fastenerassembly connecting together plies of 2, 3 and 4 ply constructions,respectively. It will be appreciated that the fastener length may bedictated by the given application.

With reference to FIGS. 29 and 30, for one embodiment a bolt 112 has ahead 120 with a No. 3 spider drive 122 or other suitable structure fordrivably engaging the bolt. A conical transition portion 124, which maybe 40°, extends a distance t for approximately 0.18 inches and tapersinto an unthreaded shank portion 126. The unthreaded shank portion 126extends to an intermediate portion wherein a threaded portion 136ultimately tapers into a gimlet point 132 at a 25°-30° angle. Thethickness h of the head 120 is approximately 0.100 inches. The threadedshank portion preferably has a minor diameter d of 0.172 inches and amajor diameter D of 0.260 inches. The thread 136 is preferably a No. 14thread with a pitch of 7.5 threads per inch.

Various bolt lengths L may be provided ranging, for example, from 2.875length to 18.00 inches. For some embodiments, the length A of thethreaded portion to the tip is 2.00 inches for each of the foregoingnoted bolt lengths L. In one embodiment wherein the length is 1.625inches, the length A is 1.250 inches. The diameter of the head 120 ispreferably 0.625 inches.

The thread 136 of the bolt is selected to threadably mate with a nut forlocking the fastening assembly in place while concurrently providing aself-drilling function. Accordingly, the bolt thread 136 has fewerthreads per inch and a greater pitch than corresponding lag bolts for asimilar fastening function. It is preferred that the pitch be less thanor equal to 8.0 threads per in.

With reference to FIGS. 18-21, nut 114 comprises a rugged cast body 140with at least two wings 142 to facilitate tightening the nut. The bodyincludes a central threaded bore 144 which is complementary with thethreads 136 of the fastener. The frontal face includes a window 146 witha minimal bolt penetration level marking 148 so that the threads may beseen in the window and a minimal thread engagement for fasteningintegrity may be ensured. The proximal end surface 150 of the nut flaresinto a large surface area and includes tooth-like projections 152 which,upon tightening, engage into the adjacent surface of the member which isto be connected. The small diameter distal end portion 154 of the nut140 includes an intermediate hexagonal or square torque surface 156 forapplying a torque to the nut or preventing the nut from rotating. Theinterior of the end portion forms an annular cavity 158. The extreme endforms an outer cylindrical (or interrupted cylindrical) surface 160which is traversed by a circumferential (or interrupted circumferential)retaining ring 162.

The cap 116 is a dome-like member which has a circular band structure170 with an internal annulus 172 which encircles a substantially conicalcavity 174. A retention recess 176 is formed at the interior of theannulus and mates with the retaining ring 162 so that the cap isgenerally retained with the end of the nut. A cylindrical extension 178mates with the walls of cavity 158 and is closely received therein inthe nut/cap position of FIGS. 18 and 19. The cap 116 is preferably amolded plastic member.

As the drill tip 132 of the fastener enters the cap 16, the drill tipthreads engage initially into the conical wall of cavity 174 (FIG. 19).As the fastener penetration continues, the cap 116 separates and islifted from the nut 114, as best illustrated in FIGS. 20 and 21. Thethreading engagement of the drill tip threads with the conical cavitycauses the cap 116 to be retained to the bolt drill tip 132. It will beappreciated that the configuration accommodates situations wherein thelength of the self-drilling bolt extends beyond the end of the nut whenthe nut is tightened and locked in position and allows for theprotective cap to, nevertheless, remain attached to the drill point.

With reference to FIGS. 22 and 23, nut 114A includes an alternativeconfiguration for the wings 142A.

With reference to FIGS. 24 and 25, the cap 216 may have an elongatedtubular form. Cap 216 is normally mounted over the end of the drill tip132 by the contractor after installation of the bolt and nut. Cap 216may be dimensioned so that for installations wherein the drill pointdoes not protrude significantly beyond the end of the nut, the cap 216is closely received in the annulus 158 of the nut. The interior of thecap includes a generally cylindrical bore 274. The walls of the bore maybe somewhat resilient. After the drill tip is threaded through and isdriven through the nut and the bolt/nut assembly tightened, the cap 216is forced onto the drill point 132. The thread 136 engages into the cap,and the extreme terminus of the tip 132 slightly pierces into theinterior end surface of the cap. If the bolt is threaded beyond the nut,the cap is correspondingly spaced from the end of the nut. Even when thedrill point protrudes substantially beyond the nut, the threadengagement into the wall of the bore 274 retains the cap over thereceived drill point to provide a protective cover, as best illustratedin FIGS. 24 and 25.

For some embodiments, such as illustrated in FIGS. 16, 26 and 27, thecap 416, 516 is integrated with the nut 414, 514 and is rigidlyattached. Accordingly, the cap defines a fixed limit for penetration ofthe drill tip which may only slightly penetrate into the end surface orbe deformed upon engagement with the interior end surface. The advantageof these embodiments is that the cap is rigidly fixed with the nut.However, if the length of the fastener is not properly selected, the nutcannot be properly tightened. In these embodiments, the window 146 isvery important to ensure that there is a minimal amount of threadingengagement between the fastener and the nut.

For some applications, as best illustrated in FIG. 28, a cap is notrequired. The drill tip 132, therefore, simply penetrates through theend of the nut 114A and may protrude substantially beyond the end of thenut. This embodiment can be advantageously employed where the protrudingbolt tips are ordinarily inaccessible.

Another embodiment of a fastener assembly is illustrated in FIGS. 31-34.The assembly employs a fastener 612 which is a bolt with a drill tip632. The shank includes an alternating series of threaded and unthreadedportions 630, 626. The threaded portion toward the distal end of thebolt tapers into the threaded drill tip 632. The head 620 includes aninternal socket drive. The unthreaded portions have a diameter between0.190 and 0.226. A chamfer 624, under the head, is configured to urgecentering of the washer. In one embodiment, the shank is coated withlubrication for better torque. The threaded tip 536 is ¾-1 inch long toaccommodate a variety of positions. The helical thread 634 of thethreaded portions has a higher thread pitch than typical wood threading.The point 633, which is designed to decrease engagement time and reducesplitting, has an angle preferably greater than or equal to 30°. In thisembodiment, the fastener is torqued through the members. The unthreadedportions 626 provide relief segments, one of which may be broken offafter the nut is threaded to the fastener.

The nut 614, as illustrated, in FIG. 32 includes a body 640 with aseries of grips or serrations 642 to facilitate grasping the nut. Thebody includes a central threaded bore 644 wherein the thread track iscomplementary with the threads on the fastener. The proximal end 650 ofthe nut includes an integrated washer 660 which spreads the load over awider surface area. The center hole 662 is perfectly matched to theunderside of the fastener to reduce tilt and off-center tendencies. Anexterior ring 666 seals around the rim of the washer 660. The serrations642 allow for a hand installation. The receiver material extends fromthe top on the nut to accept up to ½ inch in excess threading. Thewindow 646 is employed so that the threading may be inspected to ensureproper fastener penetration with the nut. A flat band is also preferablyprovided so that various information can be printed onto the nut. Thenut may be formed from plastic or other metallic materials. In someembodiments, the receiver material in the form of an insert may beformed of metal and the remainder may be formed of a plastic overmold.

With respect to FIGS. 33 and 34, a finned washer 680 may also beemployed and may be inserted up into the end of the nut in place ofwasher 660. Locking fins 690 are employed to enhance the grippingrelationship and tightening of the nut during the fastening process.

It will be appreciated that the foregoing fastener assemblies can beemployed to efficiently join adjacent the structural members under loadconditions without requiring a pre-drilling of a throughbore. Thefastener 112, 612 can be torqued and will self-tap and self-drill intothe members. After the fastener is fully driven, a nut 14, 114, 214,314, 414, 514, 614 can be threaded to the end of the bolt or the threadengagement may be commenced prior to full torquing of the bolt. Thesharp drill tip, in some embodiments, is protected by a cap 16, 116,216, 416, 516 which is designed to accommodate any length mismatchesbetween the fastener and the application that would cause the drill tip32, 132, 632 to extend beyond the end of the bolt. For some embodiments,the protruding ends of the bolt are snapped off or removed so that a capis not necessary.

The invention claimed is:
 1. A self-drilling bolt and nut assemblycomprising: a fastener having a proximal end and a distal end andcomprising a head at the proximal end including an integral washer and ashank extending from said head to a drill tip and having spaced threadedportions, said drill tip have a terminus at said distal end; a platemounted to said shank and having an upper recess dimensioned to receivesaid washer and having a lower surface with a plurality of projections;and a nut having an exterior surface configured for applying orresisting a torque and an axially extending internal threaded surfacethreadably engageable with said fastener and having a first end definingan opening for inserting said fastener and an axially spaced oppositesecond end having a cap comprising an elongated portion and a closed endand entirely enclosing said drill tip and terminus, and defining awindow between said first and second end and positioned at anintermediate axial position of said internal threaded surface, saidfirst end having a plurality of projections.
 2. The assembly of claim 1wherein said head has a hex head configuration.
 3. The assembly of claim1 wherein said drill tip has a half point configuration.
 4. The assemblyof claim 1 wherein the projections on said plate are arranged in anarcuate array.
 5. The assembly of claim 1 wherein said nut furthercomprises a pair of opposed wings.
 6. The assembly of claim 1 whereinsaid projections of said nut are arranged in an arcuate array.
 7. Theassembly of claim 1 wherein said fastener has a pitch of less than orequal to 8.0 threads per inch.
 8. The assembly of claim 1 wherein saidwindow has an elongated form and a threaded portion adjacent said drilltip has threads which are visible through said window.
 9. The assemblyof claim 8 wherein said nut has a marking on said exterior surface whichindicates a minimum thread engagement position.
 10. A self-drilling boltand nut assembly comprising: a fastener having a proximal end and adistal end and comprising a head, at the proximal end, an integralwasher and a shank extending from said head to a drill tip and having athreaded portion adjacent said drill tip, said drill tip having aterminus at said distal end; and a nut having an exterior surfaceconfigured for applying or resisting a torque and having an axial borewith an axially extending internal threaded surface threadablyengageable with said fastener, said nut having a first end defining anopening for inserting said fastener and an axially spaced oppositesecond end having a cap with an elongated cylindrical portion andentirely enclosing said drill tip and terminus and defining a windowbetween said first and second end at an intermediate axial position ofsaid internal threaded surface, so that said nut threadably receivessaid fastener, wherein a portion of said threaded portion is visiblethrough said window.
 11. The assembly of claim 10 wherein said head hasa hex head configuration.
 12. The assembly of claim 10 wherein saiddrill tip has a half point configuration.
 13. The assembly of claim 10wherein a portion of the first end of said nut is radially flared toform an end surface about said opening and projections arranged in anarcuate array extend from a plate mounted to said shank and having anupper recess dimensioned to receive said washer and having a lowersurface with said projections.
 14. The assembly of claim 13 wherein saidnut further comprises a pair of opposed wings which extend axially fromsaid radially flared portion.
 15. The assembly of claim 10 wherein saidnut has a marking at said exterior surface for indicating a minimumengagement portion of said threaded portion.
 16. The assembly of claim10 wherein said fastener has a pitch of less than or equal to 8.0threads per inch.
 17. A self-drilling bolt and nut assembly comprising:a fastener having a head including an integral washer and a shankextending from said head to a drill tip and having spaced threadedportions, said drill tip having a terminus; a plate mounted to saidshank and having an upper recess dimensioned to receive said washer andhaving a lower surface with a plurality of projections; and a nut havinga pair of opposed wings configured for applying or resisting a torqueand an exterior surface and a marking on said exterior surface whichindicates a minimum thread engagement position, said nut having anaxially extending internal threaded surface threadably engageable withsaid fastener and having a first end having a plurality of projectionsand defining an opening for inserting said fastener, and an axiallyspaced opposite second end having a cap entirely enclosing saidterminus, and defining a window of elongated form positioned at anintermediate axial position of said internal threaded surface wherein athreaded portion adjacent said drill tip has threads which are visiblethrough said window.
 18. The assembly of claim 17 wherein said fastenerhas a pitch of less than or equal to 8.0 threads per inch.
 19. Aself-drilling bolt and nut assembly comprising: a fastener having a headincluding an integral washer and a shank extending from said head to adrill tip and having a threaded portion adjacent said drill tip, saiddrill tip having a distal terminus; and a nut having an exterior surfaceconfigured for applying or resisting a torque and having an axial borewith an axially extending internal threaded surface threadablyengageable with said fastener, said nut having a first end defining anopening for inserting said fastener and an axially spaced oppositesecond end having a cap entirely enclosing said drill tip and terminusand defining a window at an intermediate axial position of said internalthreaded surface wherein a portion of the first end of said nut isflared to form an end surface about said opening and a pair of opposedwings extend axially from said flared portion, so that said nutthreadably receives said fastener, wherein portion of said threadedportion is visible through said window and said nut has a marking atsaid exterior surface for indicating a minimum engagement portion ofsaid threaded portion.
 20. The assembly of claim 19 wherein said headhas a hex head configuration.